For therapeutic use of heat in cancer therapy, it is critically important to monitor and control tissue temperature within a narrow window (˜40-45° C.) to ensure adequate therapy without complications. Hyperthermia clinics including, but not limited to, University of California San Francisco (UCSF) operate equipment such as, but not limited to, a Sonotherm 1000 (Labthermics Technologies, Champaign Ill.) 16 transducer 4×4 planar array 3.4 MHz ultrasound heating device and a Microtherm 1000 (Labthermics Technologies, Champaign Ill.) 16 antenna 4×4 planar array 915 MHz microwave heating device for applications such as, but not limited to, treating superficial tissue regions up to 15×15 cm square and as much as 4 cm deep (ultrasound) or 1.5 cm deep (microwave) below the skin.
Recently a 32 channel 915 MHz Conformal Microwave Array hyperthermia system has been approved for use in the patient clinic at University of California San Francisco and use on the first 14 patients demonstrated the ability to deliver highly adjustable heating patterns to much larger surface areas than ever before, even when the disease is spread across contoured portions of the anatomy such as the human torso.
The common problem in administering treatments with multi-element array-heating devices is gaining sufficient feedback about the tissue temperature under each independently powered heat source. The planar array microwave applicator comes with a small number of fiber-optic sensors, often less than the number of power sources, which are placed at a small number of points under the multi-element array applicator to sample the tissue temperature distribution. This small sampling of temperature is inadequate for real-time feedback control of multiple power amplifiers. For a better assessment of temperature distribution under such heating arrays, sensors may be pulled manually within special thermal mapping catheters lying on the tissue surface and temperatures recorded at 5-10 mm spaced positions across the surface. This thermal mapping procedure significantly increases the number of surface temperature measurements by providing one or more linear profiles of surface temperature under the heating array, but is tedious and time consuming to generate, and does not provide a true two dimensional characterization of surface temperature distribution.